ALD, in which temporally alternating and sequential reactant pulses of reactants are flowed into a reaction chamber, can be used to form multicomponent films, that is, films composed of thinner constituent films which have different compositions, and in which the thinner films are preferably vertically stacked in a repeating, regular sequence. By selecting the sequence and number of cycles, it has been believed that the film composition can easily be tailored in depositions using ALD.
HfSiO films are a type of film which can be grown using various ALD sequences, with HfCl4, SiCl4 and H2O used as precursors. For example, pulses of H2O flowing into a reaction chamber can be used to separate pulses of HfCl4 or SiCl4, e.g., in one cycle, a HfCl4 pulse can be followed by a H2O pulse, which is followed by a SiCl4 pulse, which is followed by a H2O pulse. The cycles can be repeated to form a film of a desired thickness.
However, it has been found that ALD can have difficulties forming films having some desired compositions. For example, it has been found that ALD has difficulties forming HfSiO films that are silicon oxide rich. Increasing the amount of silicon oxide by increasing the number of SiCl4/H2O cycles was found to have little impact on the quantity of deposited silicon oxide. After an initial cycle of SiCl4 followed by H2O, additional and subsequent SiCl4/H2O cycles were found to result in limited additional deposition. Without being limited by theory, the SiO2 deposition process by ALD is believed to be poisoned by the additional SiCl4/H2O cycles. It was found that a cycle of HfCl4 followed by H2O was needed before further SiO2 could be deposited. Moreover, attempting to increase the amount of silicon in the HfSiO film by extending the length of the SiCl4 pulses had little effect. Thus, these difficulties place severe constraints on the silicon concentrations that can be achieved in HfSiO films that are deposited by ALD.
In another example, when growing HfSiON films using HfCl4, SiCl4, NH3 and H2O as precursors in various ALD sequences, it was difficult to achieve nitrogen concentrations of 3 atomic % or higher. Without being limited by theory, it is believed that the nitride deposition utilizes a less effective chemistry than the deposition of the other film materials, thereby limiting the nitrogen concentration, since less material is deposited by this chemistry. It is also believed that nitrogen on the surface of the deposited film may be replaced by oxygen when exposed to the oxidant pulse, thereby further diminishing the nitrogen concentration. Whatever the mechanism, depending upon the chemistry and the desired deposited film, ALD has been found to have significant limitations, especially for forming multicomponent films.
In some applications, CVD provides an alternative deposition scheme. For some chemistries and types of films, however, e.g., oxide chemistries employing the hydrolysis of halides to form oxide films, CVD is expected to result in overly aggressive gas phase reactions and ALD is the preferred method of deposition. Thus, while ALD has been found to have limited ability to tailor compositions in some applications, such as in the formation of HfSiO or HfSiON films, CVD is also expected to have limited compatibility with the depositions of these films, due to overly strong gas phase hydrolysis reactions.
Moreover, it has been found that, while some chemistries are compatible with both CVD and ALD, many chemistries are more suitable for only CVD or ALD. In some cases, this can limit the combination of chemistries that can be selected for the deposition of multicomponent films. For example, depending on the materials constituting the film to be formed, all the chemistries used in the deposition of the film may need to be compatible with ALD processing or all the chemistries may need to be compatible with CVD processing. In other situations, it has been found that available chemistries may be suitable for either CVD or ALD, but some advantages can be achieved using an ALD mode of operation and other advantages can be achieved with a CVD mode of operation.
Advantageously, preferred embodiments of the invention provide a solution that overcomes the problems noted above and that provides a method that combines the advantages of an ALD mode of operation and a CVD mode of operation. For example, preferred embodiments allow the formation of multicomponent films, such as HfSiON films, with elemental concentrations which can be tailored, as desired. Moreover, using ALD and CVD-type processing allows chemistries with disparate reactivities to be combined. For example, the high reactivity of highly reactive chemistries can be controlled by using the chemistries in an ALD-type deposition, while the moderate reactivity of moderately reactive chemistries can be advantageously applied in a CVD-type deposition, which allows for increased deposition rates.
In an embodiment of the invention, a method for the deposition of multi-component thin films on a substrate in a reaction chamber is provided. The method comprises depositing a first component of the film by flowing pulses of a first and second reactant into the reaction chamber in an Atomic Layer Deposition (ALD) pattern of sequential, alternating and self limiting pulses and depositing a second component of the film by flowing a third reactant and a fourth reactant into a reactor in a pattern corresponding to a pulsed CVD pattern wherein pulses of the third reactant are flown into the reaction chamber during flowing of the fourth reactant into the reaction chamber. It will be appreciated that the terms “first,” “second,” “third,” and “fourth” are used for ease of description and do not necessarily indicate the order or identity of a reactant. For example, each of these reactants may be different, or one or more of these reactants may be the same.
In another embodiment of the invention, a method for depositing a film on a substrate is provided. The method comprises exposing the substrate to alternating and sequential reactant pulses of at least two mutually reactive reactants in an ALD mode of operation during a period A and exposing the substrate to one or more pulses of a reactant while exposing the substrate to another reactant in a pulsed CVD mode of operation during a period B, wherein the two reactants are mutually reactive.
In yet another embodiment of the invention, a method for depositing a multi-component thin film on a substrate in a reaction chamber is provided. The method comprises depositing a first component of the film on the substrate by flowing a first and second reactant into the reaction chamber in sequential and alternating pulses during a period A. The first and second reactants deposit self-limitedly on the substrate. A second component of the film is deposited on the first component by flowing a third reactant into the reaction chamber while simultaneously flowing a fourth reactant into the reaction chamber during a period B. The third and fourth reactants are mutually reactive. A total exposure time of the substrate to the fourth reactant during the period B is longer than a total exposure time of the substrate to the third reactant during the period B.
In another embodiment of the invention, a method is provided for depositing a film on a substrate. The method comprises exposing the substrate to temporally separated pulses of at least two mutually reactive reactants during a period A to deposit a compound comprising elements of the at least two mutually reactive reactants. About a monolayer or less of material is deposited per pulse. The substrate is exposed to one or more pulses of a third reactant while exposing the substrate to a fourth reactant during a period B. The third and fourth reactants are mutually reactive An interval between each of the pulses of the third reactant is at least about 1.75 times a duration of an immediately preceding pulse of the third reactant.
In yet another embodiment of the invention, a method is provided for depositing a metal compound film on a substrate. The method comprises exposing the substrate to one or more pulses of a metal source reactant while exposing the substrate to a first reactant reactive with the metal source reactant, thereby forming a film comprising a metal compound during a period A. Less than about 8 monolayers of the metal compound are deposited per pulse of the metal source reactant. The substrate is exposed to pulses of a second reactant reactive with the metal compound film during a period B. The substrate is not exposed to a metal precursor during the period B.